This month, researchers tasked with evaluating the beaked whale population in Guam’s waters deployed another set of recording instruments as part of an ongoing project. 

In 2022, the team submerged five units in the waters off the northwest corner of Guam and a sixth unit south of Guam. Then they hit record and waited.

Holger Klinck, Ph.D., is part of the team conducting the research.

“A total of 145 beaked whale encounters were registered across the two sites. Cuvier's beaked whales were by far the most common species, comprised 133 encounters and occurred almost exclusively at night,” Klinck told The Husk. 

Armed with that data and curious to know more, the team this month deployed another set of units off the coasts of Guam, but this time they’ll swap the locations, according to Klinck. 

“What we really want to know is how many beaked whales are utilizing this area and how this animal density changes throughout the year. To be able to do this, we need to figure out how likely it is that our instruments acoustically register whales that are in the vicinity,” Klinck said.

Among the many interesting things researchers learned from those 2022 recordings: A surprising number of whale encounters were recorded at night.

“It’s an interesting question as to why we only recorded them during the night. From other studies, we know that these animals produce sounds throughout the entire day. There isn’t a specific time of the day when they are more chatty. So, my best guess at this point is that they only come to these areas during the night and that they move to other areas — maybe further offshore — during the day,” he said. 

Klinck said there were also differences in animal acoustic detection based on location. 

“In the north, we hear the animals more during the spring and fall, with fewer acoustic detections during the summer. In the south, we detect the animals more frequently during the summer. So, there may be some seasonal north-south movement going on as well,” he said. 

Klinck previously said that while other areas like the Bahamas, Hawaii and Florida have an extensive network of underwater acoustic sensors, the Mariana Islands do not. So researchers have sent acoustic recorders into the ocean to monitor marine mammals in this area.

The set of acoustic recorders deployed this month will collect sounds of the sea for the next six months, according to Klinck. 

The more information researchers can collect about the beaked whale population, the better understanding they’ll have about these animals as they move about the Marianas. ✶

Past coverage

This post is a follow-up to previous reporting in The Husk. Read my past pieces below for some context.

Beaked whales near Guam and potential sonar impact to be studied Jasmine Stole Weiss · July 4, 2022 Read full story

Researchers to record beaked whales around Guam Jasmine Stole Weiss · July 10, 2022 Read full story